Ultimate lightweight wheel-motor concept
- Thread starter speedmd
- Start date
speedmd
10 MW
Hi Miles
I am no thermo expert but it looks to be a mixed bag to evaluate. We have various configurations of case material and surface finishes to start. Venting adds a whole new complexity to the equation. Air temp/ speed is critical at the heat sources and and even small amounts of it will have huge benefits in keeping temps from running away on us. Looking at the flux density color profiles of the stator cores on emetor plots, we may be able to extract a fair estimate of heat generation flow/ locations. Just a thought. Wish we had a member that could do a heat flow analysis on a open vs sealed motor and various vent configurations for us all to see.
http://www.bembook.ibpsa.us/index.php?title=Convective_heat_transfer
I am no thermo expert but it looks to be a mixed bag to evaluate. We have various configurations of case material and surface finishes to start. Venting adds a whole new complexity to the equation. Air temp/ speed is critical at the heat sources and and even small amounts of it will have huge benefits in keeping temps from running away on us. Looking at the flux density color profiles of the stator cores on emetor plots, we may be able to extract a fair estimate of heat generation flow/ locations. Just a thought. Wish we had a member that could do a heat flow analysis on a open vs sealed motor and various vent configurations for us all to see.
http://www.bembook.ibpsa.us/index.php?title=Convective_heat_transfer
speedmd
10 MW
Looks like a interesting package from deskeng.
speedmd
10 MW
Surface loss should be at least triple of static loss at normal speed (Aprox. 18-19 mph) 30klm/hr. I would say 120- 150 watts is conservative. Just a gut feel from looking at the charts.
Motor Cad sounds expensive
Motor Cad sounds expensive
liveforphysics
100 TW
Miles said:
With SH grade magnets being the temperature weak-link, I would imagine at minimum >200W.
Imagine trying to heat that whole ring to >150C with only 4 x 50w soldering irons while it's in a breeze.
The huge delta capabilities help tremendously at shedding energy. At 150C with 0.08m^2 area you will be shedding ~12W of radiated energy as well.
speedmd
10 MW
Besides being a great shape (thin pancake with lots of skin per unit volume) we have it in most likely a somewhat turbulent air flow environment.
200W make sense, I did check on Justin simulator how much a 9C is able to dissipate @ 30km/h and it can be up to 300W
This one will be way better since it is in-runner and stator can dissipate heat easily.
I will take some measurements on the brake side tonight
This one will be way better since it is in-runner and stator can dissipate heat easily.
I will take some measurements on the brake side tonight
Miles said:
So that's 94.6% at ~20mph and 93% at ~30mph (level ground, normal conditions)
Regarding regen, if it's going to be problem I'd tentatively offer the suggestion of binning it off for sake of simplicity. Geared motors don't have and even on a direct-drive motor is ~2% energy recovery really worth it?
speedmd
10 MW
I would prefer simple, light weight and zero cogging /freewheeling when off throttle. If we can add on a regen lock up clutch without adding much weight or loosing much in the mass compatibility arena then ....
What is there out there in bike world in a narrow freewheel (3-5 speed) that will slip on / adapt and fit directly on the freehub body next to this motor. Like the split freehub, but would think the standard freehub bodies will find more customers for this fantastic concept of a motor.
What is there out there in bike world in a narrow freewheel (3-5 speed) that will slip on / adapt and fit directly on the freehub body next to this motor. Like the split freehub, but would think the standard freehub bodies will find more customers for this fantastic concept of a motor.
regen % is variable depending on condition can be as low as 2% but usually is averaging 10%
read justin tests results about it.
anyways it s not a problem to usenthe freewheel side if wanted.
I am thinking about building this. maybe I can help doing details desingnmon solidworks.
casing, bearings, hall sensor, etc
read justin tests results about it.
anyways it s not a problem to usenthe freewheel side if wanted.
I am thinking about building this. maybe I can help doing details desingnmon solidworks.
casing, bearings, hall sensor, etc
speedmd said:I would prefer simple, light weight and zero cogging /freewheeling when off throttle. If we can add on a regen lock up clutch without adding much weight or loosing much in the mass compatibility arena then ....
yes, a clutch for regen would be great. do you think this will work at cassette side due to internal freewheel?
I more and more think about mounting the motor to disc brake side would be the overall better idea. regen will work like on common hubs and a normal cassette with all gears can be used.
with a shimano centerlock hub the motor could be mount very simple and also tighten
this is great.ok, the motor would be no more gearable if a hub with shift function is used, but i think this is anyway no good solution (the gears will wear down quick and overall efficiency will drop down..)
shimano saint centerlock rearhub (can be converted to 6-bolt 44mm-BCD with separate adapter):
pro:
- the motor can be mounted solid to the hub and will not wobble
- regen will work
- big cassette with all gears could be used
con:
- less width on this side of the hub
- less space between swingarm and spokes
->> more complex motor axle and flange for bearings
speedmd
10 MW
You would need a pressure /fixed plate on the spoke flange to lock up against. I still would much prefer a freewheeling bike and accept leaving stopping issues to the brakes if I had my choice. If the motor can freewheel on the brake side, I would have no issue. This motor should be able to mount that side also if desired with possibly need for some stay mods/bending. A three or five speed rear and a variable or standard crank should cover the range reasonably well with 2 plus kw at the wheel. I am near ready to jump at one just the way mile has drawn it so far but I know we have much more to bounce around here and regen is a biggie for many folks.
while brake and cassette mounting are good ideas, I was thinking about mounting it like a regular screw on pinions and add thread to be able to put on a single speed freewheel.
This way we can keep the disk brake if needed/wanted and still have regen possible.
This way we can keep the disk brake if needed/wanted and still have regen possible.
speedmd
10 MW
Thud posted his mod which is a great solution here. If there was a three - five speed version.
http://endless-sphere.com/forums/viewtopic.php?f=28&t=13862&start=25
http://endless-sphere.com/forums/viewtopic.php?f=28&t=13862&start=25
speedmd
10 MW
Perfect miles. Thanks for sharing. I am ready now! :lol: A speed drive schlumpy crank, and you have a 40 plus mph under 40 pound bike that pedals near normal when the batt runs dead.
John in CR
100 TW
Miles said:
When I was modeling heat transfer from hubbies I used 100W/m²K for the convective heat transfer coefficient, and I was in the ballpark with Justin's measured results, but that was at 30mph and higher rpm due to a smaller wheel. As Luke stated though, top shelf magnets will surely put the ability to transfer heat to a safe range, because the delta T can easily be more than doubled without heat damage. After testing with smooth covers at first, then the ability to transfer heat can easily be doubled by doubling the surface area inside and out with surface shaping. The Chinese have dropped the ball so effectively in the area of heat xfer for hubbies that room for improvement is vast. eg Even when they add surface area to the exterior of the covers, they leave the inside smooth, ignoring that the heat path has 2 air interfaces with the cover, stator-air-cover-outside air.
Regarding the complexity of a high quality rear hubbie, why complicate the design so much? On a low power ebike front wheel e-drive is so much simpler and just as functional, if not better? The ultimate wheel-motor will have proper connection to the bike and a controller with totally variable regen, so not only do the problems/issues with front drive go away, but to maximize regen recovery it needs to be on the front anyway. How many of you have ridden a front drive ebike?
I made this point about fwd for this power level earlier in the thread
Better for regen braking, etc
But people like rwd. I think if we were copying the d series motor style I would push for fwd
Now we are developing a casette motor, which has never been done before as far as I know. Much more exciting than simply copying the d series!
Super easy to add to any bike. Super easy to service...replace bearings, hall sensors, rewind (with a d series you cant pull the covers without removing spokes).
There was talk of a cassette motor years ago but now we have the skills and money and support to finally make it
Think different!
(You can mount the cassette motor on the front fork with the right mix of parts)
Better for regen braking, etc
But people like rwd. I think if we were copying the d series motor style I would push for fwd
Now we are developing a casette motor, which has never been done before as far as I know. Much more exciting than simply copying the d series!
Super easy to add to any bike. Super easy to service...replace bearings, hall sensors, rewind (with a d series you cant pull the covers without removing spokes).
There was talk of a cassette motor years ago but now we have the skills and money and support to finally make it
Think different!
(You can mount the cassette motor on the front fork with the right mix of parts)
